It was observed that the pattern of phototactic movements of the silkworm larvae varied as the larval maturity proceeded. In wandering stage, mature larvae showed a phototactic behavior moving their heads from side to side (Fig. 1B), and when offered two light sources, they moved along the mid-line between two sources (Fig. 2) .After gut purge, mature larvae showed phototaxis without the head movement shown in wandering stage (Fig. 1C), and went to one of two light sources straight from the start. The threshold for the phototactic response also varied, and the photosensitivity lowered as the maturity proceeded (Fig.3) . The optical axes and structure of stemmata were examined, and the possibility that the variations of phototactic behavior in the mature stage is connected with the change of visual function by larval-pupal development was discussed.

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We examined the relationships between O₃ sorption and the acute effects of the O₃ on sunflower leaves, such as changes in stomatal response and visible injury, using an image instrumentation method. The results obtained were as follows:
1) Changes in stomatal response to O₃ varied randomly at different sites on a leaf, and were not dependent on the integrated O₃ sorption at these sites. This result suggests that there are differences in stomatal sensitivity to O₃ among local sites on a leaf.
2) The degree of visible injury at local sites on a leaf, which reached chlorosis and necrosis, was not related to the integrated O₃ sorption at these sites. This result suggests that the differences in the degree of the visible injury among local sites on a leaf are dependent on differences not only in factors related to O₃ sorption, but also in other physiological factors among these sites.

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System identification of “plant-water” is examined by spectrum analysis, where the relationship between the input of light or relative humidity and the output of leaf temperature or water content in stem are obtained by computing frequency function or weighting function.
Furthermore to prove the method, the step re-sponse of leaf temperature and water content in stem are obtained by computing the convolution integral of both weighting function and the step input of light. Especially, the response of leaf temperature obtained by the present system identification is closely related to that actually observed, which is found to be valid on the examination of coherency.
On these findings, optimal control of water dificit and photosynthesis might be realized by monitoring leaf temperature.

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The optimal control of plant growth by monitoring leaf temperature was examined separately for the transient state from sunrise to mid-day and for the stationary state in mid-day. During the transient state, the plant suffered from water deficiency, leaf temperature fluctuated and photosynthesis decreased. To prevent such phenomena, a computer controlled system was designed and tested. That is, leaf temperature was monitored, water stress of the plant was determined by computer, and a humidifier was operated. In the plant controlled by the present system, at the time of transfer from transient to stationary state, the leaf temperature was lower and water stress less than in the plants controlled by simple programmed control. For the control at the stationary state, the relationship among leaf temperature, water stress, photosynthesis, etc., was determined from some experiments and a model. Photosynthesis was found to be greater when the plants were subjected to appropriate water stress by controlling the water supply to the roots. Based on these findings, a control system was designed and tested. That is, when the leaf temperature oscillated due to environmental changes, the water supplying system was operated so as to decrease the oscillation. After the oscillation had decreased, the water supplying system was controlled by the information which had been memorized in the computer to obtain maximum photosynthesis. By the use of this control system a 2.67 fold increase in dry matter was at-tained during 10-days cultivation as compared with the common control system.

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